fiboa · m-mohr · Aug 30, 2024 · Feb 4, 2025 · Mar 9, 2025 · Mar 9, 2025
diff --git a/.github/workflows/test.yaml b/.github/workflows/test.yaml
@@ -3,7 +3,7 @@ on:
   - push
   - pull_request
 jobs:
-  deploy:
+  docs:
     runs-on: ubuntu-latest
     steps:
       - uses: actions/setup-python@v5
@@ -15,7 +15,30 @@ jobs:
           pip install pipenv
           pipenv install
       - run: pipenv run test-docs
+  schema:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/setup-python@v5
+        with:
+          python-version: '>=3.9'
+      - uses: actions/checkout@v4
+      - name: Install pipenv
+        run: |
+          pip install pipenv
+          pipenv install
       - run: pipenv run test-schema
+  examples:
+    runs-on: ubuntu-latest
+    needs: schema
+    steps:
+      - uses: actions/setup-python@v5
+        with:
+          python-version: '>=3.9'
+      - uses: actions/checkout@v4
+      - name: Install pipenv
+        run: |
+          pip install pipenv
+          pipenv install
       - run: pipenv run test-geojson-features
       - run: pipenv run test-geojson-collection
-      - run: pipenv run test-geoparquet
+      - run: pipenv run test-geoparquet
diff --git a/CHANGELOG.md b/CHANGELOG.md
@@ -11,27 +11,34 @@ and this project adheres to [Semantic Versioning](http://semver.org/spec/v2.0.0.
 
 - Property `category`
 - Property `determination_details`
+- Information about the encoding of datatypes at the collection-level
 
 ### Changed
 
-- ...
-
-### Deprecated
-
-- ...
+- Switched from v0.1.0 to v0.2.0 of the schema language
+- Renamed `fiboa_extensions` to `schemas`
+- Schemas must be valid HTTP(S) URLs
+- GeoParquet: Renamed Parquet metadata key from `fiboa` to `collection`
+- GeoJSON: Switched `contentEncoding` for data type `binary` from `binary` to `base64`
+- GeoJSON data types: `null` is not allowed any longer, instead omit the property
+- GeoJSON FeatureCollection: Collection-level data is provided at the top-level, not in a `fiboa` property
 
 ### Removed
 
-- Value `administrative` was removed from `determination_method` in favour of the new property `category`
+- Value `administrative` was removed from `determination_method` in favor of the new property `category`
+- `fiboa_version` in favor of adding the schema URL of the specification to `schemas`.
+- GeoJSON Feature: `links` property
 
 ### Fixed
 
 - Various minor clarifications and editorial enhancements
-- GeoParquet encoding: Properties that are optional can be omitted if all values are null values
-- GeoJSON encoding: Clarify the encoding of the top-level properties (including `links` and `fiboa`)
-- GeoJSON encoding: Clarify the use of RFC 7946
-- GeoParquet encoding for bounding boxes and objects
 - Added descriptions to the allowed values for `determination_method`
+- Clarified handling of missing values
+- GeoJSON: Clarify the encoding of the top-level properties (including `links` and `fiboa`)
+- GeoJSON: Clarify the use of RFC 7946
+- GeoParquet: Properties that are optional can be omitted if all values are null values
+- GeoParquet: Added encoding for bounding boxes and objects
+- GeoParquet: Clarified the use of Map and Struct data types
 
 ## [v0.2.0] - 2024-04-10
 

diff --git a/CITATION.cff b/CITATION.cff
@@ -8,7 +8,7 @@ preferred-citation:
   type: standard
   title: "Field Boundaries for Agriculture (fiboa) specification"
   abstract: "Making field boundaries openly available in a unified way."
-  version: 0.2.0
+  version: 0.3.0
   year: 2024
   date-released: 2024-04-10
   license: Apache-2.0

diff --git a/CONTRIBUTING.md b/CONTRIBUTING.md
@@ -40,6 +40,9 @@ We use pipenv to execute the tests.
 Start with the following command in the folder where this README is located:
 `pip install pipenv --user`
 
+Install the dependencies for the test:
+`pipenv install`
+
 Finally, you can run the tests as follows:
 
 - To check the markdown run: `pipenv run test-docs`

diff --git a/README.md b/README.md
@@ -7,7 +7,7 @@ This repository contains the core specification for fiboa, including the data sc
 For more context, information on the ecosystem, and points of contact see the
 [fiboa github organization](https://github.com/fiboa/).
 
-- Version: **0.2.0**
+- Version: **0.3.0**
 
 > [!IMPORTANT]  
 > The fiboa specification is a work in progress.
@@ -29,15 +29,30 @@ The specification in this repository consists of three parts:
 - [GeoJSON Encoding](geojson/README.md)
 - [GeoParquet Encoding](geoparquet/README.md)
 
-To completent the specification, there are also best practices and extensions available:
+To complement the specification, there are also best practices and extensions available:
 
 - [Best Practices](best-practices/README.md)
 - [Extensions](https://github.com/fiboa/extensions/)
 
-The repository also contains additional information about the project:
+## Relation to other standards and working groups
 
-- [Changelog](CHANGELOG.md)
-- [Citation Details (as CFF file)](CITATION.cff)
+fiboa doesn't aim to reinvent the wheel.
+Our aim is to align with existing efforts as much as possible.
+Some parts of the specification are already based on the work of other initiatives,
+e.g. the determination-related fields in the core specification.
+
+Related standards and working groups are:
+
+- [Adapt standard](https://adaptstandard.org), including their [WG17](https://github.com/ADAPT/Standard/issues/97)
+- [Varda FieldID](https://www.varda.ag/global-field-id)
+- [Deere Boundaries](https://developer.deere.com/dev-docs/boundaries)
+- [AgGateway](https://aggateway.org/), including their
+  [Locking in on Field Boundaries](https://aggateway.org/Portals/1010/WebSite/About%20Us/FIELD%20BOUNDARY%20FLYER%20122123.pdf?ver=2024-01-03-212959-590) initiative
+
+If you think we are missing relevant work here, we'd love to hear from you.
+Please get in touch by [opening an issue](https://github.com/fiboa/specification/issues/new)!
+
+## Contributing
 
 The fiboa community strives to provide a welcoming and transparent environment for all of the project’s participants.
 You can find additional information about our community best practices and collaborative development processes below:

diff --git a/best-practices/README.md b/best-practices/README.md
@@ -7,3 +7,10 @@
 
 All properties should be using snake case.
 For example a field for a land-use class should be named `landuse_class` instead of `landuseClass`.
+
+## Extension prefixes
+
+All properties in an extensions should have a common prefix.
+Extensions commonly use the colon (`:`) as separator between prefix and property name, e.g. `crop:name`.
+A single underscore (`_`) should be avoided to avoid conflicts with other property names (see [Casing](#casing)).
+Nevertheless, the separator can be chosen freely by extension authors.
diff --git a/core/README.md b/core/README.md
@@ -1,57 +1,88 @@
-# Core Specification
+# Core Specification <!-- omit in toc -->
 
-This specification describes the core data and metadata properties for both at the
-Collection and Feature level.
+This specification describes the core data and metadata properties that describe a fiboa Feature.
+The specification doesn't distinguish between collection-level and feature-level properties,
+common definitions are shared across these levels.
 
 - A Collection refers to a group of one or more features.
 - A Feature is a single field geometry with additional properties.
 
-> [!NOTE]
-> The Core Specification is still work in progress. Feedback is welcome!
+- **Schema:** <https://fiboa.github.io/specification/v0.3.0/schema.yaml>
 
-- **Schema:** <https://fiboa.github.io/specification/v0.2.0/schema.yaml>
+## Table of Contents <!-- omit in toc -->
 
-## Schema
+- [General Properties](#general-properties)
+  - [schemas](#schemas)
+  - [id](#id)
+  - [collection](#collection)
+  - [category](#category)
+- [Spatial Properties](#spatial-properties)
+  - [area / perimeter](#area--perimeter)
+- [Determination Properties](#determination-properties)
+  - [determination\_datetime](#determination_datetime)
+  - [determination\_method](#determination_method)
+- [Schema Language](#schema-language)
 
-The data types in the following document are defined in
-[fiboa Schema](https://github.com/fiboa/schema), v0.1.0.
+## General Properties
 
-fiboa Schema defines a (limited) set of data types and a vocabulary to express
-additional constraints for these data types.
-This allows to define a clear mapping between the core specification and its encodings.
+| Property Name | Data Type                       | Description |
+| ------------- | ------------------------------- | ----------- |
+| schemas       | object\<string, array\<string>> | **REQUIRED.** A list of schemas the collection implements. |
+| id            | string                          | **REQUIRED.** An identifier for the field. |
+| collection    | string                          | **REQUIRED.** The identifier of the collection. |
+| category      | array\<string>                  | A set of categories the field boundary belongs to. |
+
+### schemas
+
+The schemas the collection implements.
+Each schema must be a valid HTTP(S) URLs to an existing YAML files compliant to fiboa Schema.
+The schema for this specification (see above) is required to be provided.
+
+Each `collection` must have a single set of applicable schemas.
+The key of the dictionary must be equal to the value provided for the `collection` property.
 
-- [Data types](https://github.com/fiboa/schema/blob/v0.1.0/datatypes.md)
-- [Vocabulary](https://github.com/fiboa/schema/blob/v0.1.0/README.md#vocabulary)
+The schema URI for fiboa that is listed above is required to be present.
 
-## Collection
+**Example for `schemas`:**
 
-Collection-level metadata must be provided in an object that contains the properties below.
-The invidiual encodings may decide to embed the collection or make it available separately.
+This describes two collections `abc` and `xyz`.
 
-### Properties
+```json
+{
+  "abc": [
+    "https://fiboa.github.io/specification/v0.3.0/schema.yaml"
+  ],
+  "xyz": [
+    "https://fiboa.github.io/specification/v0.3.0/schema.yaml",
+    "https://fiboa.github.io/crop-extension/v0.1.0/schema.yaml",
+  ]
+}
+```
 
-| Property Name    | Data Type      | Description |
-| ---------------- | -------------- | ----------- |
-| fiboa_version    | string         | **REQUIRED.** Version number of the fiboa specification this entity implements. |
-| fiboa_extensions | array\<string> | A list of URIs to extensions this entity implements. |
+### id
 
-Generally, the version and the extensions must be uniform per Collection.
+It must be unique per collection, i.e. `collection` and `id` form a unique identifier.
 
-Other properties are also allowed to be provided, but are not described by this specification.
+### collection
 
-## Features
+A collection is a group of one or more features with a unique identifier, stored in the `collection` property.
 
-### General Properties
+Encodings may support to store properties that consists of the same value across all features at the collection-level.
+This de-duplicates data for more efficient resource usage, but only applies if more than two features are available for the collection.
+The specific location and behaviour of collection-level data is specified in the encoding-specific specifications.
 
-| Property Name | Data Type      | Description |
-| ------------- | -------------- | ----------- |
-| id            | string         | **REQUIRED.** A unique identifier for the field. It must be unique within the [Collection](#collection). |
-| collection    | string         | The identifier of the parent collection. |
-| category      | array\<string> | A set of categories the field boundary belongs to. |
+**Example:**
 
-**collection:** The collection identifier is usually only needed for merged datasets.
+You have two different field boundary datasets named `abc` (CC-0 licensed) and `xyz` (CC-BY-4.0 licensed).
+If you store the datasets separately, you can store the license in the collection-level data
+as the value for the property is the same for all features.
+Once you merged the two datasets, you must ensure that a unique identifier for the collection is provieded
+(here: `abc` and `xyz`) so that IDs are unique.
+Additionally, you have to add the license property on the feature-level as the licenses are now twofold.
 
-**category:** Choose any (unique) combination of the following values:
+### category
+
+Choose any (unique) combination of the following values:
 
 - `conceptual`: This boundary represents how the grower thinks of a field, and what they would share with service
   providers to allocate information at the highest level of the field concept within their operation.
@@ -65,7 +96,7 @@ Other properties are also allowed to be provided, but are not described by this
 
 The categories are based on the [definitions of the AgGateway initiative](https://aggateway.org/Portals/1010/WebSite/About%20Us/FIELD%20BOUNDARY%20FLYER%20122123.pdf?ver=2024-01-03-212959-590).
 
-### Spatial Properties
+## Spatial Properties
 
 | Property Name | Data Type    | Description |
 | ------------- | ------------ | ----------- |
@@ -74,29 +105,36 @@ The categories are based on the [definitions of the AgGateway initiative](https:
 | area          | float        | Area of the field, in hectares. Must be > 0 and <= 100,000. |
 | perimeter     | float        | Perimeter of the field, in meters. Must be > 0 and <= 125,000. |
 
-**area/perimeter:** These are derived attributes from the geometry itself,
+### area / perimeter
+
+These are derived attributes from the geometry itself,
 and must match the geometry's area/perimeter. If they do not match then the
 geometry should be considered canonical.
 Validators may flag the value as invalid if it exceeds a certain threshold.
 
-### Determination Properties
+## Determination Properties
 
-| Property Name          | Data Type | Description                                                  |
-| ---------------------- | --------- | ------------------------------------------------------------ |
-| determination_method   | string    | The boundary creation method, one of the values below.       |
-| determination_datetime | datetime  | The last timestamp at which the field did exist and was observed, in UTC. |
+| Property Name          | Data Type | Description |
+| ---------------------- | --------- | ----------- |
+| determination_method   | string    | The boundary creation method, one of the values below. |
+| determination_datetime | datetime  | The last timestamp at which the field did exist and was observed. |
 | determination_details  | string    | Further details about the determination, especially the methodology. |
 
-**determination_datetime**: In case the source of the information is an
-interval or a set of timestamps, use the end.
+### determination_datetime
+
+The last timestamp at which the field did exist and was observed, provided in the UTC timezone.
+
+In case the source of the information is an interval or a set of timestamps, use the end.
 For example, for ML you'd use the timestamp of the last image and not the
 timestamp of the actual execution.
 
 > [!NOTE]  
 > We define more temporal properties in the
 > [timestamps extension](https://github.com/fiboa/timestamps).
 
-**determination_method**: Must be one of the following values:
+### determination_method
+
+The determination method must be one of the following values:
 
 - `manual`: Hand created from imagery, e.g. using a tool to point and click on a map.
 - `surveyed`: Determined through a professional land survey measuring the actual distances and angles on the ground.
@@ -107,3 +145,15 @@ timestamp of the actual execution.
 
 The determination methods are based on the definitions of the [AgGateway initiative - WG17](https://aggateway.org/).
 The specific values have [not been published yet](https://github.com/fiboa/specification/issues/31).
+
+## Schema Language
+
+The schema language used for fiboa is [fiboa Schema](https://github.com/fiboa/schema), version 0.2.0.
+
+The data types in the tables above are defined in the document
+[Data Types](https://github.com/fiboa/schema/blob/v0.2.0/datatypes.md).
+
+fiboa Schema defines a (limited) set of data types and a
+[vocabulary](https://github.com/fiboa/schema/blob/v0.2.0/README.md#vocabulary)
+to express additional constraints for these data types.
+This allows to define a clear mapping between the core specification and its encodings.
diff --git a/core/schema/schema.yaml b/core/schema/schema.yaml
@@ -1,8 +1,25 @@
-$schema: https://fiboa.github.io/schema/v0.1.0/schema.json
+$schema: https://fiboa.github.io/schema/v0.3.0/schema.json
 required:
+  - schemas
   - id
+  - collection
   - geometry
+collection:
+  schemas: true
+  id: false
+  geometry: false
+  bbox: false
 properties:
+  schemas:
+    type: array
+    items:
+      type: string
+      format: uri
+      pattern: ^https?://
+    contains:
+      type: string
+      enum:
+        - https://fiboa.github.io/specification/v0.3.0/schema.yaml
   id:
     type: string
     minLength: 1

diff --git a/geojson/README.md b/geojson/README.md
@@ -1,62 +1,73 @@
 # GeoJSON Encoding Specification
 
-The GeoJSON encoding defines how field boundaries compliant to fiboa must be published.
-The generic GeoJSON format is defined in
-[IETF RFC 7946](https://datatracker.ietf.org/doc/html/rfc7946).
+The GeoJSON encoding defines to encode field boundaries compliant to fiboa as
+GeoJSON as defined in [IETF RFC7946](https://datatracker.ietf.org/doc/html/rfc7946).
 
-> [!NOTE]
-> The GeoJSON encoding is still work in progress. Feedback is welcome!
+A single fiboa Feature must be encoded as a GeoJSON [`Feature`](#feature).
+Multiple fiboa Featurs should be provided as a GeoJSON [`FeatureCollection`](#featurecollection).
+Other GeoJSON types are not allowed.
 
-- **[Examples](examples/):**
-  1. [as a FeatureCollection](examples/featurecollection/features.json)
-  2. [as individual Features with a dedicated Collection](examples/individual-features/)
-- **[Datatype mapping](datatypes.md)**
+Related documents:
 
-## Collection
+- [Examples](examples/)
+- [Datatype mapping](datatypes.md)
 
-A [fiboa Collection](../core/README.md#collection) must be provided as a JSON object, either
-1. embedded into the GeoJSON in a top-level property named `fiboa` (see example 1), or
-2. separately as a JSON file that is linked to from the GeoJSON (see example 2).
+## Feature
 
-A fiboa Collection may be a [GeoJSON FeatureCollection](https://datatracker.ietf.org/doc/html/rfc7946#section-3.3).
-All features in a FeatureCollection must be fiboa-compliant.
+- Example: [individual features](examples/individual-features/)
 
-## Features
-
-Each [fiboa Feature](../core/README.md#features) must be a valid
+Each [fiboa Feature](../core/README.md) must be a valid
 [GeoJSON Feature](https://datatracker.ietf.org/doc/html/rfc7946#section-3.2).
 
 The following properties are defined for a GeoJSON Feature (at the top-level of the object):
 
-| Property Name | Data Type           | Description                                                  |
-| ------------- | ------------------- | ------------------------------------------------------------ |
-| id            | string              | **REQUIRED. ** See [id](../core/README.md#general-properties) in the core specification, must not be a `number` |
-| type          | string              | **REQUIRED. ** The GeoJSON type, must be: `Feature`          |
+| Property Name | Data Type           | Description |
+| ------------- | ------------------- | ----------- |
+| id            | string              | **REQUIRED.** See [id](../core/README.md#id) in the core specification, must not be a `number` |
+| type          | string              | **REQUIRED.** The GeoJSON type, must be: `Feature` |
 | geometry      | object              | **REQUIRED.** A [GeoJSON Geometry Object](https://datatracker.ietf.org/doc/html/rfc7946#section-3.1), must not be `null` |
 | bbox          | array\<number>      | A [GeoJSON Bounding Box](https://datatracker.ietf.org/doc/html/rfc7946#section-5) |
-| properties    | object              | An object with additional properties (see [`properties`](#properties)) |
-| links         | array\<Link Object> | A list of links (see [`links`](#links))                      |
-| fiboa         | object              | An object with the [fiboa Collection](../core/README.md#collection) properties if not provided as a link (see [Collection](#collection)). |
+| properties    | object              | An object with all additional properties (see [`properties`](#properties)) |
+
+The mapping between the Parquet data types and the fiboa data types, can be found in the
+[data type mapping](datatypes.md).
 
 > [!IMPORTANT]  
 > RFC 7946 doesn't support a property named `crs`, which was only available in an earlier version of GeoJSON (2008).
 > The CRS of the GeoJSON geometry and bbox must be WGS 84 / OGC CRS 84,
-> see the [RFC 7946, chapter 4](https://datatracker.ietf.org/doc/html/rfc7946#section-4) for details. 
+> see the [RFC 7946, chapter 4](https://datatracker.ietf.org/doc/html/rfc7946#section-4) for details.
 
-### `properties`
+[Collection-level](../core/README.md#collection) data is not supported.
+All properties are provides in the JSON object with the key [`properties`](#properties).
 
-Must include any property that is required by the fiboa core specification (currently none).
+### properties
+
+Must include any property that is required by the fiboa core specification.
 May include any additional property.
 All properties defined by the core specification (except for `id`, `geometry` and `bbox`) or extensions should be provided here.
 
-### `links`
+## FeatureCollection
+
+- Example: [a feature collection](examples/featurecollection/features.json)
+
+All features in a GeoJSON FeatureCollection must be fiboa-compliant.
+
+Properties can also be stored at the [collection-level](../core/README.md#collection)
+if all values for a specific property have the same value in all features.
+This de-duplicates data for more efficient resource usage.
+All properties are stored on the top-level of the FeatureCollection object as
+[foreign members](https://datatracker.ietf.org/doc/html/rfc7946#section-6.1).
+The individual features shall not contain any properties that are stored at the collection-level.
+Validation must ensure that the collection-level properties are taken into account.
+
+The following properties in Features can't be collection-level properties:
 
-An array of links where each link conforms to the
-[Hyperlink Schema](http://schemas.opengis.net/ogcapi/common/part1/1.0/openapi/schemas/link.yaml)
-defined in
-[OGC API - Common - Part 1](https://docs.ogc.org/is/19-072/19-072.html#_11b9b4f7-42fc-413a-b63a-e7fb060b5e4b).
+- `id`
+- `geometry`
+- `bbox`
 
-The following relation types are commonly used:
+Properties with the following names can#t be moved to the collection-level due to conflicts with the
+FeatureCollection properties defined by GeoJSON:
 
-- `self`: Absolute link to the GeoJSON file itself.
-- `collection`: Link to the [Collection](#collection)
+- `features`
+- `type`
diff --git a/geojson/datatypes.md b/geojson/datatypes.md
@@ -3,28 +3,33 @@
 The following table shows the data types that are used by fiboa in the Property definitions.
 It also shows the mapping to the GeoJSON data types.
 
-| fiboa data type                                     | (Geo)JSON                                                    |
-| --------------------------------------------------- | ------------------------------------------------------------ |
-| boolean                                             | boolean                                                      |
-| int8                                                | integer<br />minimum: -128<br />maximum: 127                 |
-| uint8                                               | integer<br />minimum: 0<br />maximum: 255                    |
-| int16                                               | integer<br />minimum: -32768<br />maximum: 32767             |
-| uint16                                              | integer<br />minimum: 0<br />maximum: 65535                  |
-| int32                                               | integer<br />minimum: -2147483648<br />maximum: 2147483647   |
-| uint32                                              | integer<br />minimum: 0<br />maximum: 4294967295             |
-| int64                                               | integer<br />minimum: -9223372036854775808<br />maximum: 9223372036854775807 |
-| uint64                                              | integer<br />minimum: 0<br />maximum: 18446744073709551615   |
-| float<br />IEEE 32-bit                              | number<br />minimum: ?<br />maximum: ?                       |
-| double<br />IEEE 64-bit                             | number<br />minimum: ?<br />maximum: ?                       |
-| binary                                              | string<br />contentEncoding: binary                          |
-| string<br />charset: UTF-8                          | string                                                       |
-| array                                               | array                                                        |
-| object<br />keys: string<br />values: any           | object<br />additionalProperties: false                      |
-| date                                                | string<br />format: date                                     |
-| date-time<br />with milliseconds<br />timezone: UTC | string<br />format: date-time<br />pattern: Z$               |
-| geometry                                            | [object with schema](https://geojson.org/schema/Geometry.json) |
-| bounding-box<br />x and y only, no z                | array<br />minItems: 4<br />maxItems: 4<br />items: number   |
-| *required* (not a datatype)                         | null                                                         |
+| fiboa data type                                     | (Geo)JSON                                                    | Collection-level |
+| --------------------------------------------------- | ------------------------------------------------------------ | ---------------- |
+| boolean                                             | boolean                                                      | yes              |
+| int8                                                | integer<br />minimum: -128<br />maximum: 127                 | yes              |
+| uint8                                               | integer<br />minimum: 0<br />maximum: 255                    | yes              |
+| int16                                               | integer<br />minimum: -32768<br />maximum: 32767             | yes              |
+| uint16                                              | integer<br />minimum: 0<br />maximum: 65535                  | yes              |
+| int32                                               | integer<br />minimum: -2147483648<br />maximum: 2147483647   | yes              |
+| uint32                                              | integer<br />minimum: 0<br />maximum: 4294967295             | yes              |
+| int64                                               | integer<br />minimum: -9223372036854775808<br />maximum: 9223372036854775807 | yes |
+| uint64                                              | integer<br />minimum: 0<br />maximum: 18446744073709551615   | yes              |
+| float<br />IEEE 32-bit                              | number<br />minimum: ?<br />maximum: ?                       | yes              |
+| double<br />IEEE 64-bit                             | number<br />minimum: ?<br />maximum: ?                       | yes              |
+| binary                                              | string<br />contentEncoding: base64                          | yes              |
+| string<br />charset: UTF-8                          | string                                                       | yes              |
+| array                                               | array                                                        | yes              |
+| object<br />keys: string<br />values: any           | object<br />additionalProperties: false                      | yes              |
+| date                                                | string<br />format: date                                     | yes              |
+| date-time<br />with milliseconds<br />timezone: UTC | string<br />format: date-time<br />pattern: Z$               | yes              |
+| geometry                                            | [object with schema](https://geojson.org/schema/Geometry.json) | no             |
+| bounding-box<br />x and y only, no z                | array<br />minItems: 4<br />maxItems: 4<br />items: number   | no               |
+
+## Missing values
+
+For optional properties, values might be missing.
+This is expressed by omitting the JSON property.
+The value `null` is not allowed.
 
 ## Potential issues in conversion
 

diff --git a/geojson/examples/featurecollection/features.json b/geojson/examples/featurecollection/features.json
@@ -1,4 +1,15 @@
 {
+  "schemas": {
+    "de_nrw": [
+      "https://fiboa.github.io/specification/v0.3.0/schema.yaml",
+      "https://fiboa.github.io/inspire-extension/v0.2.0/schema.yaml",
+      "https://fiboa.github.io/flik-extension/v0.1.0/schema.yaml",
+      "https://fiboa.github.io/crop-extension/v0.1.0/schema.yaml"
+    ]
+  },
+  "collection": "de_nrw",
+  "license": "dl-de/by-2-0",
+  "attribution": "Land Nordrhein-Westfalen / Open.NRW - https://www.opengeodata.nrw.de/produkte/umwelt_klima/bodennutzung/landwirtschaft/",
   "type": "FeatureCollection",
   "features": [
     {
@@ -8,158 +19,63 @@
         "inspire:id": "https://geodaten.nrw.de/id/inspire-lc-fb/landcoverunit/12324",
         "flik": "DENWLI0542130247",
         "determination_datetime": "2005-02-28T00:00:00Z",
-        "nutz_code": "A",
-        "nutz_txt": "Ackerland",
-        "area": 1.631100058555603
+        "crop:code": "A",
+        "crop:name": "Ackerland",
+        "area": 1.6311
       },
       "geometry": {
         "type": "Polygon",
         "coordinates": [
           [
-            [
-              7.875243329949302,
-              51.7469574917968
-            ],
-            [
-              7.8754156210171224,
-              51.74865579902567
-            ],
-            [
-              7.87559517961007,
-              51.748657516128716
-            ],
-            [
-              7.875727139469757,
-              51.74864762337336
-            ],
-            [
-              7.875865723118926,
-              51.74861179149097
-            ],
-            [
-              7.876160946694515,
-              51.74853656922356
-            ],
-            [
-              7.876274940061089,
-              51.748526513043004
-            ],
-            [
-              7.876646213349393,
-              51.74852263605798
-            ],
-            [
-              7.876669177898854,
-              51.74759587524452
-            ],
-            [
-              7.876683221091441,
-              51.7470291214554
-            ],
-            [
-              7.875243329949302,
-              51.7469574917968
-            ]
+            [7.8752433, 51.7469574],
+            [7.8754156, 51.7486557],
+            [7.8755951, 51.7486575],
+            [7.8757271, 51.7486476],
+            [7.8758657, 51.7486117],
+            [7.8761609, 51.7485365],
+            [7.8762749, 51.7485265],
+            [7.8766462, 51.7485226],
+            [7.8766691, 51.7475958],
+            [7.8766832, 51.7470291],
+            [7.8752433, 51.7469574]
           ]
         ]
       },
-      "bbox": [
-        7.875243329949302,
-        51.7469574917968,
-        7.876683221091441,
-        51.748657516128716
-      ]
+      "bbox": [7.8752433, 51.7469574, 7.8766832, 51.7486575]
     },
     {
       "id": "2713",
       "type": "Feature",
       "properties": {
         "inspire:id": "https://geodaten.nrw.de/id/inspire-lc-fb/landcoverunit/2713",
         "flik": "DENWLI0540210084",
-        "determination_datetime": "2005-02-28T00:00:00Z",
-        "nutz_code": "A",
-        "nutz_txt": "Ackerland",
-        "area": 1.8975000381469727
+        "determination_datetime": "2005-02-22T00:00:00Z",
+        "crop:code": "W",
+        "crop:name": "Weide",
+        "area": 1.8975
       },
       "geometry": {
         "type": "Polygon",
         "coordinates": [
           [
-            [
-              9.279072225112648,
-              51.925508828714925
-            ],
-            [
-              9.279848170539884,
-              51.92582918268683
-            ],
-            [
-              9.280173032315249,
-              51.925963048968214
-            ],
-            [
-              9.280599939130775,
-              51.92614034991495
-            ],
-            [
-              9.280660193987938,
-              51.926028714865886
-            ],
-            [
-              9.280886077078973,
-              51.9256102896548
-            ],
-            [
-              9.281335286046785,
-              51.924778127406576
-            ],
-            [
-              9.281305739341624,
-              51.92472580957354
-            ],
-            [
-              9.280917027691007,
-              51.92458295033388
-            ],
-            [
-              9.279903540966059,
-              51.92421337118715
-            ],
-            [
-              9.279817610187122,
-              51.92423316888092
-            ],
-            [
-              9.279398358118248,
-              51.92501015234708
-            ],
-            [
-              9.279241344298002,
-              51.925301083950984
-            ],
-            [
-              9.279072225112648,
-              51.925508828714925
-            ]
+            [9.2790722, 51.9255088],
+            [9.2798481, 51.9258291],
+            [9.280173, 51.925963],
+            [9.2805999, 51.9261403],
+            [9.2806601, 51.9260287],
+            [9.280886, 51.9256102],
+            [9.2813352, 51.9247781],
+            [9.2813057, 51.9247258],
+            [9.280917, 51.9245829],
+            [9.2799035, 51.9242133],
+            [9.2798176, 51.9242331],
+            [9.2793983, 51.9250101],
+            [9.2792413, 51.925301],
+            [9.2790722, 51.9255088]
           ]
         ]
       },
-      "bbox": [
-        9.279072225112648,
-        51.92421337118715,
-        9.281335286046785,
-        51.92614034991495
-      ]
+      "bbox": [9.2790722, 51.9242133, 9.2813352, 51.9261403]
     }
-  ],
-  "fiboa": {
-    "fiboa_version": "0.2.0",
-    "fiboa_extensions": [
-      "https://fiboa.github.io/inspire-extension/v0.2.0/schema.yaml"
-    ],
-    "id": "de_nrw",
-    "title": "Field boundaries for North Rhine-Westphalia (NRW), Germany",
-    "license": "dl-de/by-2-0",
-    "attribution": "Land Nordrhein-Westfalen / Open.NRW - https://www.opengeodata.nrw.de/produkte/umwelt_klima/bodennutzung/landwirtschaft/"
-  }
-}
+  ]
+}
diff --git a/geojson/examples/individual-features/12324.json b/geojson/examples/individual-features/12324.json
@@ -2,68 +2,35 @@
   "id": "12324",
   "type": "Feature",
   "properties": {
+    "schemas": {
+      "example": [
+        "https://fiboa.github.io/specification/v0.3.0/schema.yaml",
+        "https://fiboa.github.io/flik-extension/v0.1.0/schema.yaml"
+      ]
+    },
+    "collection": "example",
     "flik": "DENWLI0542130247",
     "determination_datetime": "2005-02-28T00:00:00Z",
     "nutz_code": "A",
     "nutz_txt": "Ackerland",
-    "area": 1.631100058555603
+    "area": 1.6311
   },
   "geometry": {
     "type": "Polygon",
     "coordinates": [
       [
-        [
-          7.875243329949302,
-          51.7469574917968
-        ],
-        [
-          7.8754156210171224,
-          51.74865579902567
-        ],
-        [
-          7.87559517961007,
-          51.748657516128716
-        ],
-        [
-          7.875727139469757,
-          51.74864762337336
-        ],
-        [
-          7.875865723118926,
-          51.74861179149097
-        ],
-        [
-          7.876160946694515,
-          51.74853656922356
-        ],
-        [
-          7.876274940061089,
-          51.748526513043004
-        ],
-        [
-          7.876646213349393,
-          51.74852263605798
-        ],
-        [
-          7.876669177898854,
-          51.74759587524452
-        ],
-        [
-          7.876683221091441,
-          51.7470291214554
-        ],
-        [
-          7.875243329949302,
-          51.7469574917968
-        ]
+        [7.8752433, 51.7469574],
+        [7.8754156, 51.7486557],
+        [7.8755951, 51.7486575],
+        [7.8757271, 51.7486476],
+        [7.8758657, 51.7486117],
+        [7.8761609, 51.7485365],
+        [7.8762749, 51.7485265],
+        [7.8766462, 51.7485226],
+        [7.8766691, 51.7475958],
+        [7.8766832, 51.7470291],
+        [7.8752433, 51.7469574]
       ]
     ]
-  },
-  "links": [
-    {
-      "href": "collection.json",
-      "rel": "collection",
-      "type": "application/json"
-    }
-  ]
-}
+  }
+}
diff --git a/geojson/examples/individual-features/2713.json b/geojson/examples/individual-features/2713.json
@@ -2,80 +2,41 @@
   "id": "2713",
   "type": "Feature",
   "properties": {
+    "schemas": {
+      "example": [
+        "https://fiboa.github.io/specification/v0.3.0/schema.yaml",
+        "https://fiboa.github.io/flik-extension/v0.1.0/schema.yaml"
+      ]
+    },
+    "collection": "example",
     "flik": "DENWLI0540210084",
     "determination_datetime": "2005-02-28T00:00:00Z",
     "nutz_code": "A",
     "nutz_txt": "Ackerland",
-    "area": 1.8975000381469727
+    "area": 1.8975000
   },
   "geometry": {
     "type": "Polygon",
     "coordinates": [
       [
-        [
-          9.279072225112648,
-          51.925508828714925
-        ],
-        [
-          9.279848170539884,
-          51.92582918268683
-        ],
-        [
-          9.280173032315249,
-          51.925963048968214
-        ],
-        [
-          9.280599939130775,
-          51.92614034991495
-        ],
-        [
-          9.280660193987938,
-          51.926028714865886
-        ],
-        [
-          9.280886077078973,
-          51.9256102896548
-        ],
-        [
-          9.281335286046785,
-          51.924778127406576
-        ],
-        [
-          9.281305739341624,
-          51.92472580957354
-        ],
-        [
-          9.280917027691007,
-          51.92458295033388
-        ],
-        [
-          9.279903540966059,
-          51.92421337118715
-        ],
-        [
-          9.279817610187122,
-          51.92423316888092
-        ],
-        [
-          9.279398358118248,
-          51.92501015234708
-        ],
-        [
-          9.279241344298002,
-          51.925301083950984
-        ],
-        [
-          9.279072225112648,
-          51.925508828714925
-        ]
+        [9.2790722, 51.9255088],
+        [9.2798481, 51.9258291],
+        [9.2801730, 51.9259630],
+        [9.2805999, 51.9261403],
+        [9.2806601, 51.9260287],
+        [9.2808860, 51.9256102],
+        [9.2813352, 51.9247781],
+        [9.2813057, 51.9247258],
+        [9.2809170, 51.9245829],
+        [9.2799035, 51.9242133],
+        [9.2798176, 51.9242331],
+        [9.2793983, 51.9250101],
+        [9.2792413, 51.9253010],
+        [9.2790722, 51.9255088]
       ]
     ]
   },
-  "links": [
-    {
-      "href": "collection.json",
-      "rel": "collection",
-      "type": "application/json"
-    }
+  "bbox": [
+    9.2790722, 51.9242133, 9.2813352, 51.9261403
   ]
-}
+}
diff --git a/geojson/examples/individual-features/collection.json b/geojson/examples/individual-features/collection.json
diff --git a/geojson/schema/datatypes.json b/geojson/schema/datatypes.json
@@ -1,6 +1,6 @@
 {
   "$schema": "https://json-schema.org/draft/2020-12/schema",
-  "$id": "https://fiboa.github.io/specification/v0.2.0/geojson/datatypes.json",
+  "$id": "https://fiboa.github.io/specification/v0.3.0/geojson/datatypes.json",
   "$defs": {
     "boolean": {
       "type": "boolean"

diff --git a/geoparquet/README.md b/geoparquet/README.md
@@ -1,33 +1,33 @@
 # GeoParquet Encoding Specification
 
 The Geoparquet encoding defines how field boundaries compliant to fiboa must be published.
-The generic GeoParquet format is defined in the
-[OGC GeoParquet specification v1.0.0](https://geoparquet.org/releases/v1.0.0/).
+The generic GeoParquet format is defined in the OGC GeoParquet specification,
+either version [v1.0.0](https://geoparquet.org/releases/v1.0.0/)
+or [v1.1.0](https://geoparquet.org/releases/v1.1.0/).
 We aim to support any future version of GeoParquet, too.
 
-> [!NOTE]
-> The GeoParquet encoding is still work in progress. Feedback is welcome!
-
-- **[Examples](examples/)**
-- **[Data type mapping](datatypes.md)**
-
-## Collection
-
-The GeoParquet file must embed the [fiboa Collection](../core/README.md#collection)
-in the Parquet metadata in a property named `fiboa`.
-
-It is recommended to additionally provide the fiboa Collection as a separate JSON file, too.
-
-## Features
-
-Each [fiboa Feature](../core/README.md#features) corresponds to a row in a GeoParquet file.
+Each [fiboa Feature](../core/README.md) corresponds to a row in a GeoParquet file.
 
 The properties defined for fiboa Features are made available as individual columns in the GeoParquet file.
 
 Properties that are optional can be omitted if all values are
 [null values](https://parquet.apache.org/docs/file-format/nulls/),
 i.e. the column can be missing from the GeoParquet file.
 
+Properties can also be stored at the [collection-level](../core/README.md#collection) if all values in a column have the same value.
+This de-duplicates data for more efficient resource usage and simplifies the sturcture of the Parquet file.
+The GeoParquet file must embed the properties in the Parquet metadata in a property named `collection`.
+The metadata must be JSON-encoded.
+
 The mapping between the Parquet data types and the fiboa data types, can be found in the
 [data type mapping](datatypes.md).
 
+Related documents:
+
+- [Examples](examples/)
+- [Data type mapping](datatypes.md)
+
+## Best practices
+
+For data with a lot of repetition, brotli compression is recommended.
+This applies particularly for merged datasets that don't deduplicate properties to the collection-level.
diff --git a/geoparquet/datatypes.md b/geoparquet/datatypes.md
@@ -3,32 +3,45 @@
 The following table shows the data types that are used by fiboa in the Property definitions.
 It also shows the mapping to the GeoParquet data types.
 
-| fiboa Schema data type                              | (Geo)Parquet                                                 |
-| --------------------------------------------------- | ------------------------------------------------------------ |
-| boolean                                             | BOOLEAN                                                      |
-| int8                                                | IntType<br />bitWidth: 8<br />isSigned: true<br />(deprecated: INT_8) |
-| uint8                                               | IntType<br />bitWidth: 8<br />isSigned: false<br />(deprecated: UINT_8) |
-| int16                                               | IntType<br />bitWidth: 16<br />isSigned: true<br />(deprecated: INT_16) |
-| uint16                                              | IntType<br />bitWidth: 16<br />isSigned: false<br />(deprecated: UINT_16) |
-| int32                                               | IntType<br />bitWidth: 32<br />isSigned: true<br />(deprecated: INT_32) |
-| uint32                                              | IntType<br />bitWidth: 64<br />isSigned: false<br />(deprecated: UINT_32) |
-| int64                                               | IntType<br />bitWidth: 64<br />isSigned: true<br />(deprecated: INT_64) |
-| uint64                                              | IntType<br />bitWidth: 64<br />isSigned: false<br />(deprecated: UINT_64) |
-| float<br />IEEE 32-bit                              | FLOAT                                                        |
-| double<br />IEEE 64-bit                             | DOUBLE                                                       |
-| binary                                              | BYTE_ARRAY                                                   |
-| string<br />charset: UTF-8                          | STRING (BYTE_ARRAY)                                          |
-| array                                               | LIST                                                         |
-| object<br />keys: string<br />values: any           | STRUCT / MAP                                                 |
-| date                                                | DATE (INT32)                                                 |
-| date-time<br />with milliseconds<br />timezone: UTC | TimestampType (INT64)<br />isAdjustedToUTC: true<br />unit:  MILLIS<br />(deprecated: TIMESTAMP_MILLIS) |
-| geometry                                            | BYTE_ARRAY<br />encoded as WKB                               |
-| bounding-box<br />x and y only, no z                | STRUCT(xmin FLOAT, ymin FLOAT, xmax FLOAT, ymax FLOAT)       |
-| *if a field is not required*                        | [Nullity](https://parquet.apache.org/docs/file-format/nulls/) |
+| fiboa Schema data type                              | (Geo)Parquet                                                 | Collection-level                |
+| --------------------------------------------------- | ------------------------------------------------------------ | ------------------------------- |
+| boolean                                             | BOOLEAN                                                      | yes                             |
+| int8                                                | IntType<br />bitWidth: 8<br />isSigned: true<br />(deprecated: INT_8) | yes                             |
+| uint8                                               | IntType<br />bitWidth: 8<br />isSigned: false<br />(deprecated: UINT_8) | yes                             |
+| int16                                               | IntType<br />bitWidth: 16<br />isSigned: true<br />(deprecated: INT_16) | yes                             |
+| uint16                                              | IntType<br />bitWidth: 16<br />isSigned: false<br />(deprecated: UINT_16) | yes                             |
+| int32                                               | IntType<br />bitWidth: 32<br />isSigned: true<br />(deprecated: INT_32) | yes                             |
+| uint32                                              | IntType<br />bitWidth: 64<br />isSigned: false<br />(deprecated: UINT_32) | yes                             |
+| int64                                               | IntType<br />bitWidth: 64<br />isSigned: true<br />(deprecated: INT_64) | yes                             |
+| uint64                                              | IntType<br />bitWidth: 64<br />isSigned: false<br />(deprecated: UINT_64) | yes                             |
+| float<br />IEEE 32-bit                              | FLOAT                                                        | yes                             |
+| double<br />IEEE 64-bit                             | DOUBLE                                                       | yes                             |
+| binary                                              | BYTE_ARRAY                                                   | as string, base64-encoded       |
+| string<br />charset: UTF-8                          | STRING (BYTE_ARRAY)                                          | yes                             |
+| array                                               | LIST                                                         | yes                             |
+| object<br />keys: string<br />values: any           | STRUCT or MAP (see below)                                    | yes                             |
+| date                                                | DATE (INT32)                                                 | as string, compliant to ISO8601 |
+| date-time<br />with milliseconds<br />timezone: UTC | TimestampType (INT64)<br />isAdjustedToUTC: true<br />unit:  MILLIS<br />(deprecated: TIMESTAMP_MILLIS) | as string, compliant to ISO8601 |
+| geometry                                            | BYTE_ARRAY<br />encoded as WKB                               | no                              |
+| bounding-box<br />x and y only, no z                | STRUCT(xmin FLOAT, ymin FLOAT, xmax FLOAT, ymax FLOAT)       | no                              |
 
 The integer data types and the data type string can also be mapped to the ENUM data type in Parquet
 if a pre-defined set of values is available.
 
+## Missing values
+
+For optional properties, values might be missing.
+This is expressed by providing the values `null`
+(see data type [Nullity](https://parquet.apache.org/docs/file-format/nulls/)).
+
+## Struct vs Map
+
+Parquet has both Map and Struct types. The struct type is similar to a named dictionary while the map type is similar to a list of ordered (key, value) pairs. The main difference is that you need to know up-front the keys for the struct type, while you don't for the map type.
+
+Due to this difference, the **Struct** type can only be used if `additionalProperties` is `false` (the default value) and only `properties` is provided to clearly specify the exact names of the properties.
+
+Any variability in the keys through the use of `additionalProperties` (except for the default `false`) or `patternProperties` requires the use of the **Map** data type. Please note that the order of the Map type is guaranteed to be preserved.
+
 ## Unsupported Data Types
 
 The following data types occur in Parquet, but are not currently supported in fiboa:
@@ -45,4 +58,4 @@ The following data types occur in Parquet, but are not currently supported in fi
 
 ## Potential issues in conversion
 
-- The micro/nanosecond precision of Datetime / Times may got lost
+- The micro/nanosecond precision of Datetime / Times may get lost